Deep-sea hydrothermal metallic sulfide deposits are metallic mineral resources with a strategic significance in modern times, including metallic elements such as iron, copper, lead, zinc, nickel, cobalt, gold, silver, platinum. Those deposits are distributed in global oceans from hundreds of meters to 4,000 meters deep, and are mainly focused at mid-ocean ridges, back-arc basins and formation mobile fault zones. According to preliminary estimates, some 900 individual hydrothermal metallic sulfide deposits are totally cultivated at the sea floors of the oceans in the world, and some 160 deposits have been found at present. The preliminary estimates on the deposits at several mid-ocean ridges show that the scale usually ranges from 1 million tons to 0.1 billion tons, which reflects that hydrothermal deposits have a considerable resource inventory. Compared with deep-sea polymetallic nodules or cobalt-rich crusts, the sea-floor hydrothermal sulfides have advantages of small water depth, high quality, easy exploitation, beneficiation and smelting. Therefore, the investigation, research and development activities are significant for human society which faces resources shortages increasingly.
In the 1960s, the development of sea-floor metallic sources boomed, including polymetallic nodules, cobalt-rich crusts and hydrothermal metallic sulfide deposits. A great progress has been made after decades of research and development. Even so, there are still difficulties in the exploitation of the deep-sea metallic sulfides at present, mainly including the following aspects. 1) High exploitation cost: The quality of the sea-floor sulfides is high, but if the sea-floor sulfides does not reach a certain exploitation scale, the cost is inevitably higher than the land exploitation, and the cost in the ore transport and in the recycling and smelting of metals such as silver, copper, zinc, lead, etc. are also relatively high. 2) Conventional concept and immature technologies: The exploitation technologies and experience of the deep-sea polymetallic nodules, cobalt-rich crusts and deep-sea oil gases can only serve as references of the exploitation of the hydrothermal sulfides, so new approaches are in need, and aiming at the formation features of the sea-floor deposit, innovative ideas are required to design more reasonable and pertinent exploration and exploitation solutions. 3) Environmental risks: Once submarine mining enters the implementation stage, risks will be inevitably brought to the marine environment, including water pollution and submarine landslide, in particular possible damage to the unique biotic and ecological communities of the hydrothermal zones, thus resulting in ecological disasters.